使用 VS 2010、C#、.NET 3.5
我有三个用户定义的 Web 控件：
控件 1 有一个 ListBox 和一个 Button
控制 2 有 3 Text-Boxes2DropDownLists和 3Buttons
控件 3 只有一个在代码中填充的表。
我有两页：
第 1 页有控制 2 和控制 3
第 2 页有控制 1、控制 2 和控制 3
Control 2 的功能在第 1 页上完美运行。
但是，在第 2 页上单击提交按钮时，DropDownLists 总是显示SelectedIndex = 0和SelectedValue = "0".
单击控件 2 上的提交按钮时，所有三个文本框和按钮在两个页面上都保留其值。只有 DropDownLists 无法保留其值。
作为参考，这里是提交按钮 OnClick 事件中的代码：
protected void btnSubmit_Click(object sender, EventArgs e)
{
clsLog.WriteLog("TrainingForm.ascx - Submit.");
tcCategoryError.Text = " ";
tcDateError.Text = " ";
tcDescriptionError.Text = " ";
tcHoursError.Text = " ";
tcMethodError.Text = " ";
foreach (Control c in this.Controls)
{
LogControls(c);
}
c_iTID = Convert.ToInt32(hTID.Value);
c_szUserName = hUserName.Value;
bool bValid = true;
DateTime dtTrainingDate = DateTime.MinValue;
string szTrainingDescription = "";
decimal dHours = 0M;
int iCategoryID = 0;
int iMethodID = 0;
if (!DateTime.TryParse(txtTrainingDate.Text, out dtTrainingDate))
{
bValid = false;
tcDateError.Text = "Please Enter Valid Training Date";
}
if (!decimal.TryParse(txtTrainingHours.Text, out dHours))
{
bValid = false;
tcHoursError.Text = "Please Enter Valid Training Hours";
}
if (this.ddlCategory.SelectedValue == "0")
{
bValid = false;
tcCategoryError.Text = "Please Select Training Category";
}
else
iCategoryID = Convert.ToInt32(this.ddlCategory.SelectedValue);
if (this.ddlTrainingMethod.SelectedValue == "0")
{
bValid = false;
tcMethodError.Text = "Please Select Training Method";
}
else
iMethodID = Convert.ToInt32(this.ddlTrainingMethod.SelectedValue);
if (txtTrainingDescription.Text.Trim() == "")
{
bValid = false;
tcDescriptionError.Text = "Please Enter Training description.";
}
else
szTrainingDescription = txtTrainingDescription.Text.Trim();
if (bValid)
{
clsData.UpdateTraining(c_iTID, "", c_szUserName, dtTrainingDate, szTrainingDescription, iCategoryID, dHours, iMethodID);
TrainingID = 0;
ClearForm();
}
OnEvent(new MyEventArgs(c_szUserName));
}
填充 DropDowns 的代码（用户定义控件的一部分）
protected void BindddlCategory(int iCategoryID)
{
DataTable dt = clsData.GetTrainingCategories();
ddlCategory.Items.Clear();
ddlCategory.AppendDataBoundItems = true;
ddlCategory.Items.Add(new ListItem("Select Training Category", "0"));
ddlCategory.DataSource = dt;
ddlCategory.DataTextField = "TrainingCategory";
ddlCategory.DataValueField = "CID";
ddlCategory.DataBind();
if (iCategoryID != 0)
ddlCategory.SelectedValue = iCategoryID.ToString();
}
protected void BindddlCategory()
{
BindddlCategory(0);
}
protected void BindddlTrainingMethod(int iMethodID)
{
DataTable dt = clsData.GetTrainingMethods();
ddlTrainingMethod.Items.Clear();
ddlTrainingMethod.AppendDataBoundItems = true;
ddlTrainingMethod.Items.Add(new ListItem("Select Training Method", "0"));
ddlTrainingMethod.DataSource = dt;
ddlTrainingMethod.DataTextField = "TrainingCategory";
ddlTrainingMethod.DataValueField = "CID";
ddlTrainingMethod.DataBind();
if (iMethodID != 0)
ddlTrainingMethod.SelectedValue = iMethodID.ToString();
}
protected void BindddlTrainingMethod()
{
BindddlTrainingMethod(0);
}
仅供参考，DDL 不会在页面加载时填充，而是在触发显示控件形式的事件时隐式填充：
public void ShowTrainingEntry(int iTrainingID)
{
clsLog.WriteLog("TrainingForm.ascx - ShowTrainingEntry(" + iTrainingID.ToString() + ")");
hTID.Value = iTrainingID.ToString();
hUserName.Value = UserName;
int iCategoryID = 0;
int iMethodID = 0;
if (iTrainingID != 0)
{
DataTable dt = clsData.GetTrainingRecord(iTrainingID);
if (dt.Rows.Count == 1)
{
txtTrainingDate.Text = Convert.ToDateTime(dt.Rows[0]["TrainingDate"]).ToString("MM/dd/yyyy");
txtTrainingHours.Text = Convert.ToDecimal(dt.Rows[0]["Hours"]).ToString("N1");
txtTrainingDescription.Text = dt.Rows[0]["TrainingDescription"].ToString();
int.TryParse(dt.Rows[0]["CategoryCID"].ToString(), out iCategoryID);
int.TryParse(dt.Rows[0]["MethodCID"].ToString(), out iMethodID);
}
ShowChangeMessage(iCategoryID == 0 | iMethodID == 0);
ShowDeleteButton(true);
ShowCancelButton(true);
}
BindddlCategory(iCategoryID);
BindddlTrainingMethod(iMethodID);
tblMain.Visible = true;
}
有人对为什么会这样有任何想法吗？
谢谢，约翰